README.rdoc

ActsAsTaggableOn

This plugin was originally based on Acts as Taggable on Steroids by
Jonathan Viney. It has evolved substantially since that point, but all
credit goes to him for the initial tagging functionality that so many
people have used.

For instance, in a social network, a user might have tags that are called
skills, interests, sports, and more. There is no real way to differentiate
between tags and so an implementation of this type is not possible with
acts as taggable on steroids.

Enter Acts as Taggable On. Rather than tying functionality to a specific
keyword (namely “tags”), acts as taggable on allows you to specify an
arbitrary number of tag “contexts” that can be used locally or in
combination in the same way steroids was used.

Installation

Plugin

Acts As Taggable On is available both as a gem and as a traditional plugin.
For the traditional plugin you can install like so (Rails 2.1 or later):

Finding Tagged Objects

Acts As Taggable On utilizes Rails 2.1's named_scope to create an
association for tags. This way you can mix and match to filter down your
results, and it also improves compatibility with the will_paginate gem: